This invention pertains to the art of power and signal distribution and, more particularly, to a communication power distribution system with current limiting capabilities.
The invention is particularly applicable to controlling fiber-to-the-curb distribution of power and transmission of signals from a central office to a desired destination in accordance with existing electric code requirements. However, it is to be appreciated that the application has broader applications and may be advantageously employed in other power distribution environments and uses.
In supplying power to end users such as homes, businesses, etc., electrical safety considerations need to be addressed. The National Electric Safety Code allows the distribution of power on a "utility right of way." The term "utility right of way" as used in this context is meant to define the geographic area where utility companies have the right to run power lines, prior to entry into homes, businesses, etc. When this distributed power is led off the "utility right of way", into a home, business, etc. other regulations take effect, such as those set forth in the National Electric Code (see for example table 725-31B, National Electric Code, 1993 Edition).
One type of communication power distribution system is set forth in FIG. 1, which illustrates a typical set-up of a fiber-to-the-curb distribution system. Optical fiber, OF, connects the central office, CO, to the host digital terminal, HDT. The central office is a main switching location and the host digital terminal is an intermediate device which provides remote switching capabilities. Optical fiber, OF, is also used to connect the host digital terminal, EDT, to individual optical network units, ONU. Each optical network unit, ON:, supplies individual lines to a number of users. In this example configuration, an ONU which supplies 12 lines will be used to service four end users (i.e. 3 lines per end user). It is to be appreciated, however, that while in this example 3 lines are provided for an end user, different numbers of lines may be provided.
The local power hub, LPH, supplies power to each of the optical network units, ONUS, via conductors such as 2-pair wire, W.
In the example of FIG. 1, the LPH is on the "utility right of way", and the ONUs supplied by the LPH are off the "utility right of way". Therefore, the output of the LPH must be within parameters set forth in existing code regulations. However, once the distribution system leaves the "utility right of way" other code regulations must be followed.
Prior art systems such as that shown in FIG. 2 have achieved the required power distribution by relying on individual power supplies, PS, to feed each ONU with limited power. Such a system increases the physical size of the local power hub and also increases the cost by requiring a plurality of individual power supplies.
The present invention contemplates a new and improved power distribution system which utilizes a bulk rectifier, and limits power by use of active current limit devices in order to overcome the above-referenced problems and others, and to provide an economically feasible installation.